Digital terrestrial television
Digital terrestrial television is a technological evolution of broadcast television and an advancement over analog television. A terrestrial implementation of digital television uses a aerial to broadcast to a conventional television antenna instead of a satellite dish or cable television connection. The amount of data that can be transmitted is directly affected by channel capacity, the modulation method in DVB-T is COFDM with either 64 or 16-state Quadrature Amplitude Modulation. In general, a 64QAM channel is capable of transmitting a bit rate. 16 and 64QAM constellations can be combined in a single multiplex, the DVB-T standard is not used for terrestrial digital television in North America. Instead, the ATSC standard calls for 8VSB modulation, which has similar characteristics to the vestigial sideband modulation used for analog television. This provides considerably more immunity to interference, but is not immune — as DVB-T is — to multipath distortion, both systems use the MPEG transport stream and H.
262/MPEG-2 Part 2 video codec specified in MPEG-2, they differ significantly in how related services are encoded. DTTV is received either via a digital set-top box, TV gateway or integrated tuner included with television sets, some set-top-boxes and TV gateways include digital video recorder functionality. This is quite common in the UK, see external links, indoor aerials are even more likely to be affected by these issues and possibly need replacing. Main articles, List of digital television deployments by country, Digital television transition Afghanistan started digital transmissions in MPEG-4 on Sunday,31 August 2014, Afghanistan adopted DVB-T2 system for digital television. India adopted DVB-T system for television in July 1999. The first DVB-T transmission was started on 26 January 2003 in the four metropolitan cities by Doordarshan. Currently the terrestrial transmission is available in digital and analog formats. 4 high power DVB-T transmitters were set up in the top 4 cities, an additional 190 high power, and 400 low power DVB-T2 transmitters have been approved for Tier I, II and III cities of the country by 2017.
The Indian telecom regulator, TRAI, had recommended the I&B to allow private broadcast companies to use the DTT technology, so far, the Indian I&B ministry only permits private broadcast companies to use satellite, cable and IPTV based systems. Israel started digital transmissions in MPEG-4 on Sunday,2 August 2009, Israel was the first nation in the Middle East and the first non-European nation to shut down its analogue TV distribution system. The new service which is operated by the Second Authority for Radio, according to government decisions, the system will expand to include two additional multiplexes that will carry new channels and HD versions of the existing channels. In this matter nothing has been decided upon until the end on 2012, on 20 March 2013 it was announced that Thomson Broadcast had won a major contract with The Second Authority for Television and Radio for the extension of its nationwide DVB-T/DVB-T2 network
San Francisco, officially the City and County of San Francisco, is the cultural and financial center of Northern California. It is the birthplace of the United Nations, the California Gold Rush of 1849 brought rapid growth, making it the largest city on the West Coast at the time. San Francisco became a consolidated city-county in 1856, after three-quarters of the city was destroyed by the 1906 earthquake and fire, San Francisco was quickly rebuilt, hosting the Panama-Pacific International Exposition nine years later. In World War II, San Francisco was a port of embarkation for service members shipping out to the Pacific Theater. Politically, the city votes strongly along liberal Democratic Party lines, San Francisco is the headquarters of five major banking institutions and various other companies such as Levi Strauss & Co. Dolby, Weebly, Pacific Gas and Electric Company, Pinterest, Uber, Mozilla, Wikimedia Foundation, as of 2016, San Francisco is ranked high on world liveability rankings.
The earliest archaeological evidence of habitation of the territory of the city of San Francisco dates to 3000 BC. Upon independence from Spain in 1821, the became part of Mexico. Under Mexican rule, the system gradually ended, and its lands became privatized. In 1835, Englishman William Richardson erected the first independent homestead, together with Alcalde Francisco de Haro, he laid out a street plan for the expanded settlement, and the town, named Yerba Buena, began to attract American settlers. Commodore John D. Sloat claimed California for the United States on July 7,1846, during the Mexican–American War, montgomery arrived to claim Yerba Buena two days later. Yerba Buena was renamed San Francisco on January 30 of the next year, despite its attractive location as a port and naval base, San Francisco was still a small settlement with inhospitable geography. The California Gold Rush brought a flood of treasure seekers, with their sourdough bread in tow, prospectors accumulated in San Francisco over rival Benicia, raising the population from 1,000 in 1848 to 25,000 by December 1849.
The promise of fabulous riches was so strong that crews on arriving vessels deserted and rushed off to the gold fields, leaving behind a forest of masts in San Francisco harbor. Some of these approximately 500 abandoned ships were used at times as storeships and hotels, many were left to rot, by 1851 the harbor was extended out into the bay by wharves while buildings were erected on piles among the ships. By 1870 Yerba Buena Cove had been filled to create new land, buried ships are occasionally exposed when foundations are dug for new buildings. California was quickly granted statehood in 1850 and the U. S. military built Fort Point at the Golden Gate, silver discoveries, including the Comstock Lode in Nevada in 1859, further drove rapid population growth. With hordes of fortune seekers streaming through the city, lawlessness was common, and the Barbary Coast section of town gained notoriety as a haven for criminals, entrepreneurs sought to capitalize on the wealth generated by the Gold Rush
California is the most populous state in the United States and the third most extensive by area. Located on the western coast of the U. S, California is bordered by the other U. S. states of Oregon and Arizona and shares an international border with the Mexican state of Baja California. Los Angeles is Californias most populous city, and the second largest after New York City. The Los Angeles Area and the San Francisco Bay Area are the nations second- and fifth-most populous urban regions, California has the nations most populous county, Los Angeles County, and its largest county by area, San Bernardino County. The Central Valley, an agricultural area, dominates the states center. What is now California was first settled by various Native American tribes before being explored by a number of European expeditions during the 16th and 17th centuries, the Spanish Empire claimed it as part of Alta California in their New Spain colony. The area became a part of Mexico in 1821 following its war for independence.
The western portion of Alta California was organized as the State of California, the California Gold Rush starting in 1848 led to dramatic social and demographic changes, with large-scale emigration from the east and abroad with an accompanying economic boom. If it were a country, California would be the 6th largest economy in the world, fifty-eight percent of the states economy is centered on finance, real estate services and professional, scientific and technical business services. Although it accounts for only 1.5 percent of the states economy, the story of Calafia is recorded in a 1510 work The Adventures of Esplandián, written as a sequel to Amadis de Gaula by Spanish adventure writer Garci Rodríguez de Montalvo. The kingdom of Queen Calafia, according to Montalvo, was said to be a land inhabited by griffins and other strange beasts. This conventional wisdom that California was an island, with maps drawn to reflect this belief, shortened forms of the states name include CA, Cal. Calif. and US-CA.
Settled by successive waves of arrivals during the last 10,000 years, various estimates of the native population range from 100,000 to 300,000. The Indigenous peoples of California included more than 70 distinct groups of Native Americans, ranging from large, settled populations living on the coast to groups in the interior. California groups were diverse in their organization with bands, villages. Trade and military alliances fostered many social and economic relationships among the diverse groups, the first European effort to explore the coast as far north as the Russian River was a Spanish sailing expedition, led by Portuguese captain Juan Rodríguez Cabrillo, in 1542. Some 37 years English explorer Francis Drake explored and claimed a portion of the California coast in 1579. Spanish traders made unintended visits with the Manila galleons on their trips from the Philippines beginning in 1565
National Educational Television
National Educational Television was an American educational broadcast television network that was owned by the Ford Foundation and co-owned by the Corporation for Public Broadcasting. The network was founded as the Educational Television and Radio Center in November 1952 by a grant from the Ford Foundations Fund for Adult Education. It was originally a service for exchanging and distributing educational television programs produced by local television stations to other stations. In the spring of 1954, ETRC moved its operations to Ann Arbor, Michigan and it put together a daily five-hour package of television programs, distributing them primarily on kinescope film to the affiliated stations by mail. The programming was noted for treating subjects in depth, including interviews with people of literary. The programming was noted for being dry and academic, with little consideration given to entertainment value. Many of the shows were designed as adult education, and ETRC was nicknamed the University of the Air, the centers headquarters moved from Ann Arbor to New York City in 1958, and the organization became known as the National Educational Television and Radio Center.
The center became more aggressive at this time, aiming to ascend to the role of the U. S. fourth television network, among its efforts, the network began importing programs from the BBC into the United States, starting with An Age of Kings in 1961. It increased its output to ten hours a week. The organization changed tactics again in November 1963 and it renamed itself National Educational Television, and spun off its radio assets. Under the centerpiece program NET Journal, NET began to air controversial, hard-hitting documentaries that explored numerous social issues of the day such as poverty and racism. While praised by critics, many affiliates, especially those in politically and culturally conservative markets, in 1966, NETs viability came into question when the Ford Foundation decided to begin withdrawing financial support because of NETs continual need for additional funding. In the meantime, the affiliated stations kept the network afloat by developing reliable sources of revenue, the U. S.
government intervened and created the Corporation for Public Broadcasting in 1967 to fund the network for the time being. However, the CPBs intent was to create its own broadcasting network. The CPB embarked on that course of action because many NET affiliates were alienated by the programming that the network offered and these affiliates further felt that NETs simultaneous production and distribution of programming constituted a conflict of interest. The Public Broadcasting Service first began operations in 1969, with NET continuing to produce several programs, however, NETs refusal to stop airing the critically praised but controversial documentaries led to Ford and the CPB deciding to shut the network down. In early 1970, both threatened to cut their funding unless NET merged its operations with Newark, New Jersey public television station WNDT-TV, on October 5,1970, PBS officially began broadcasting after NET and WNDT-TV completed their merger. WNDTs call sign was changed to WNET shortly afterward, some programs that began their runs on NET, such as Washington Week and Sesame Street, continue to air on PBS today
Effective radiated power
Effective radiated power, synonymous with equivalent radiated power, is an IEEE standardized definition of directional radio frequency power transmitted from a theoretical half-wave dipole antenna. It is differentiated from effective isotropic radiated power mainly by use of antenna gain instead of absolute gain in the calculation. The term antenna gain is assumed to be absolute unless specifically stated to be relative, the gain is multiplied by the power actually accepted by the antenna to result in the actual ERP value. Power losses which occur prior to the antenna, e. g. in the line or from inefficiency in the generator itself are therefore not included in the calculation of ERP or EIRP. Antenna gain is closely related to directivity and often used interchangeably. However, gain is less than directivity by a factor called radiation efficiency. Whereas directivity is entirely a function of wavelength and the geometry and type of antenna, accelerating charge causes electromagnetic radiation per Maxwells equations.
Therefore, antennas use a current distribution on radiating elements to generate electromagnetic energy that propagates away from the antenna and this coupling is never 100% efficient, and therefore antenna gain will always be less than directivity by this efficiency factor. The receiver would not be able to determine a difference, maximum directivity of an ideal half-wave dipole is a constant, i. e.0 dBd =2.15 dBi. Therefore, ERP is always 2.15 dB less than EIRP, the ideal dipole antenna could be further replaced by an isotropic radiator, and the receiver cannot know the difference so long as the input power is increased by 2.15 dB. Unfortunately, the distinction between dBd and dBi is often left unstated and the reader is forced to infer which was used. For example, a Yagi-Uda antenna is constructed from several dipoles arranged at intervals to create better energy focusing than a simple dipole. Since it is constructed from dipoles, often its antenna gain is expressed in dBd, obviously this ambiguity is undesirable with respect to engineering specifications.
A Yagi-Uda antennas maximum directivity is 8.77 dBd =10.92 dBi and its gain necessarily must be less than this by the factor η, which must be negative in units of dB. Neither ERP nor EIRP can be calculated without knowledge of the power accepted by the antenna, let us assume a 100 Watt transmitter with losses of 6 dB prior to the antenna. ERP <22. 77dBW and EIRP <24. 92dBW, polarization has not been taken into account so far, but properly it must be. When considering the dipole radiator previously we assumed that it was aligned with the receiver. Now assume, that the antenna is circularly polarized
Oakland /ˈoʊklənd/ is the largest city and the county seat of Alameda County, United States. The city was incorporated in 1852, Oaklands territory covers what was once a mosaic of California coastal terrace prairie, oak woodland, and north coastal scrub. Its land served as a resource when its hillside oak and redwood timber were logged to build San Francisco. In the late 1860s, Oakland was selected as the terminal of the Transcontinental Railroad. Following the 1906 San Francisco earthquake, many San Francisco citizens moved to Oakland, enlarging the citys population, increasing its housing stock and it continued to grow in the 20th century with its busy port, and a thriving automobile manufacturing industry. Oakland is known for its sustainability practices, including a top-ranking for usage of electricity from renewable resources, in addition, due to a steady influx of immigrants during the 20th century, along with thousands of African-American war-industry workers who relocated from the Deep South during the 1940s.
Oakland is the most ethnically diverse city in the country. The earliest known inhabitants were the Huchiun Indians, who lived there for thousands of years, the Huchiun belonged to a linguistic grouping called the Ohlone. In Oakland, they were concentrated around Lake Merritt and Temescal Creek, in 1772, the area that became Oakland was claimed, with the rest of California, by Spanish settlers for the King of Spain. In the early 19th century, the Spanish crown granted the East Bay area to Luis María Peralta for his Rancho San Antonio, the grant was confirmed by the successor Mexican republic upon its independence from Spain. Upon his death in 1842, Peralta divided his land among his four sons, Most of Oakland fell within the shares given to Antonio Maria and Vicente. The portion of the parcel that is now Oakland was called encinal—Spanish for oak grove—due to the oak forest that covered the area. In 1851, three men—Horace Carpentier, Edson Adams, and Andrew Moon—began developing what is now downtown Oakland, on May 4,1852, the Town of Oakland incorporated.
Two years later, on March 25,1854, Oakland re-incorporated as the City of Oakland, with Horace Carpentier elected the first mayor, the city and its environs quickly grew with the railroads, becoming a major rail terminal in the late 1860s and 1870s. In 1868, the Central Pacific constructed the Oakland Long Wharf at Oakland Point, a number of horsecar and cable car lines were constructed in Oakland during the latter half of the 19th century. The first electric streetcar set out from Oakland to Berkeley in 1891, at the time of incorporation, Oakland consisted of the territory that lay south of todays major intersection of San Pablo Avenue and Fourteenth Street. The city gradually annexed farmlands and settlements to the east and the north, Oaklands rise to industrial prominence, and its subsequent need for a seaport, led to the digging of a shipping and tidal channel in 1902. This resulted in the town of Alameda being made an island
Salinas /səˈliːnəs/ is the county seat and largest municipality of Monterey County, California. Salinas is located just outside the portion of the greater Bay Area and 10 miles east-southeast of the mouth of the Salinas River. The population was 155,662 as of 2013, the city is located at the mouth of the Salinas Valley roughly eight miles from the Pacific Ocean and has a climate more influenced by the ocean than the hot-summer interior. The marine climate is ideal for the industry, grape vineyards. Salinas is known for its vibrant and large industry and as the hometown of writer and Nobel Prize in Literature laureate John Steinbeck. The land currently occupied by the city of Salinas is thought to have settled by Native Americans known as the Esselen prior to 200 AD. Between 200 and 500 AD, they were displaced by the Rumsen group of Ohlone speaking people, before this time, Monterey was the capital of California and had been under military rule after the signing of the Treaty of Guadalupe-Hidalgo at the end of the Mexican-American war.
In the 1850s a junction of two main stage coach routes was located 18 miles east of Monterey and along the big bend of what is referred to as the Alisal Slough. Soon thereafter, in 1856, an inn called the Halfway House was opened at that junction in Salinas. The streets of Salinas were laid out in 1867, and the town was incorporated in 1874. The conversion of grazing land to crops and the coming of the road in 1868 to transport goods and people was a major turning point in the history. Dry farming of wheat and other grains as well as potatoes, irrigation changed farming in Salinas to mainly row crops of root vegetables and sugar beets. Many major vegetable producers placed their headquarters in Salinas, the camp opened on April 27,1942 and held a total of 3,608 people before closing two months on July 4. Following World War II major urban and suburban development converted much farmland to city, the city experienced two particularly strong growth spurts in the 1950s and 1960s, and again in the 1990s and early 2000s.
The Harden Ranch and Williams Ranch neighborhoods constituting much of the citys North-East were built almost exclusively between 1990 and 2004, Salinas was the birthplace of writer and Nobel Prize laureate John Steinbeck. The historic downtown, known as Oldtown Salinas, features much fine Victorian architecture, and is home to the National Steinbeck Center, the Steinbeck House, major development took place in the 1990s, with the construction of Creekbridge, Williams Ranch, and Harden Ranch. When annexed in 1963, Alisal was described as a large Mexican-American enclave, hispanic immigration peaked from the 1980s through the early 2000s. Mostly European-American neighborhoods in North Salinas, an expansion of the city built mostly in the 1950s and 60s
The City of Monterey in Monterey County is located on the southern edge of Monterey Bay, in the Northern Portion of Californias Central Coast. It stands at an elevation of 26 feet above sea level, the 2010 census recorded a population of 27,810. Monterey was the capital of Alta California under both Spain and Mexico and it was the only port of entry for taxable goods in California. In 1846 the U. S. flag was raised over the Customs House, the city had Californias first theater, public building, public library, publicly funded school, printing press, and newspaper. The city and surrounding area have attracted artists since the late 19th century, until the 1950s, there was an abundant fishery. Among Montereys notable present-day attractions are the Monterey Bay Aquarium, Cannery Row, Fishermans Wharf, long before the arrival of Spanish explorers, the Rumsen Ohlone tribe, one of seven linguistically distinct Ohlone groups in California, inhabited the area now known as Monterey. They subsisted by hunting and gathering food on and around the biologically rich Monterey Peninsula, researchers have found a number of shell middens in the area and, based on the archaeological evidence, concluded the Ohlones primary marine food consisted at various times of mussels and abalone.
A number of sites have been located along about 12 miles of rocky coast on the Monterey Peninsula from the current site of Fishermans Wharf in Monterey to Carmel. In 1602, Spanish maritime explorer Sebastian Vizcaino recorded the name Bahía de Monterrey, Vizcaino landed at the southern end of the bay and described a great port, suitable for use as an anchorage by southbound Manila galleons. Vizcaino noted and named the Point of Pines, all other uses of the name Monterey derive from Vizcainos name for the bay. Variants of the name are recorded as Monte Rey and Montery. In 1769, the first European land exploration of Alta California, for some reason, the explorers failed to recognize the place when they came to it on October 1,1769. The party continued north as far as San Francisco Bay before turning back, on the return journey, they camped near one of Montereys lagoons on November 27, still not convinced they had found the place Vizcaino had described. Franciscan missionary Juan Crespí noted in his diary, We halted in sight of the Point of Pines and camped near a lagoon which has rather muddy water.
Portolá returned by land to Monterey the next year, having concluded that he must have been at Vizcainos Port of Monterey after all, the land party was met at Monterey by Junípero Serra who traveled by sea. Portolá erected the Presidio of Monterey to defend the port and, on June 3,1770, Portolá returned to Mexico, replaced in Monterey by Captain Pedro Fages, who had been third in command on the exploratory expeditions. Fages became the governor of Alta California, serving from 1770 to 1774. Serras missionary aims soon came into conflict with Fages and the soldiers, the existing wood and adobe building became the chapel for the Presidio
San Francisco Bay Area
The San Francisco Bay Area is a populous region surrounding the San Francisco and San Pablo estuaries in Northern California. The region encompasses the cities and metropolitan areas of San Jose, San Francisco. The Bay Areas nine counties are Alameda, Contra Costa, Napa, San Francisco, San Mateo, Santa Clara and Sonoma. The combined statistical area of the region is the second-largest in California, the fifth-largest in the United States, the Bay Area has the second-most Fortune 500 Companies in the United States, and is known for its natural beauty, liberal politics and diversity. The eastern side of the bay, consisting of Alameda and Contra Costa counties, is known locally as the East Bay, the inner East Bay is more densely populated, with generally older buildings, and a more ethnically diverse population. The word Lamorinda was coined by combining the names of the cities it includes, Moraga, walnut Creek is situated east of Lamorinda and north of the San Ramon Valley and, together with Concord and Pleasant Hill comprises Central Contra Costa County.
The cities of Antioch, Brentwood and the areas surrounding them comprise East Contra Costa County. The Tri-Valley consists of the Amador, the Livermore, and the San Ramon Valleys and Pleasanton comprise the Amador Valley, Livermore lies in the Livermore Valley, and the San Ramon Valley consists of Alamo, Danville and its namesake, San Ramon. The outer East Bay is connected to the inner East Bay by BART, Interstate 580 to the south, and State Routes State Route 4 to the north, the outer East Bays infrastructure was mostly built up after World War II. This area remains largely white demographically, although the Hispanic and Filipino populations have grown significantly over the past 2–3 decades, the region north of the Golden Gate Bridge is known locally as the North Bay. This area encompasses Marin County, Sonoma County, Napa County, the city of Fairfield, being part of Solano County, is often considered the easternmost city of the North Bay. With few exceptions, this region is affluent, Marin County is ranked as the wealthiest in the state.
The North Bay is relatively rural compared to the remainder of the Bay Area, with areas of undeveloped open space, farmland. Santa Rosa in Sonoma County is the North Bays largest city, with a population of 167,815 and a Metropolitan Statistical Area population of 466,891, making it the fifth-largest city in the Bay Area. The North Bay is the section of the Bay Area that is not currently served by a commuter rail service. The area from San Francisco to the Silicon Valley, geographically part of the San Francisco Peninsula, is known locally as The Peninsula, many of these families are of foreign background and have significantly contributed to the diversity of the area. Whereas the term peninsula technically refers to the entire geographical San Franciscan Peninsula, in local terms, San Francisco is surrounded by water on three sides, the north and west. The city squeezes roughly 870,000 people in under 47 square miles, on any given day, there can be as many as 1 million people in the city because of the commuting population and tourism
In broadcasting and radio communications, a call sign is a unique designation for a transmitter station. In North America, they are used for all FCC licensed transmitters, a call sign can be formally assigned by a government agency, informally adopted by individuals or organizations, or even cryptographically encoded to disguise a stations identity. The use of signs as unique identifiers dates to the landline railroad telegraph system. Because there was only one line linking all railroad stations. In order to time, two-letter identifiers were adopted for this purpose. This pattern continued in operation, radio companies initially assigned two-letter identifiers to coastal stations and stations aboard ships at sea. These were not globally unique, so a company identifier was added. Merchant and naval vessels are assigned call signs by their national licensing authorities, in the case of states such as Liberia or Panama, which are flags of convenience for ship registration, call signs for larger vessels consist of the national prefix plus three letters.
United States merchant vessels are given call signs beginning with the letters W or K while US naval ships are assigned callsigns beginning with N, leisure craft with VHF radios may not be assigned call signs, in which case the name of the vessel is used instead. Ships in the US wishing to have a radio licence anyway are under F. C. C, class SA, Ship recreational or voluntarily equipped. Those calls follow the land mobile format of the initial letter K or W followed by 1 or 2 letters followed by 3 or 4 numbers. U. S. Coast Guard small boats have a number that is shown on both bows in which the first two digits indicate the length of the boat in feet. For example, Coast Guard 47021 refers to the 21st in the series of 47 foot motor lifeboats, the call sign might be abbreviated to the final two or three numbers during operations, for example, Coast Guard zero two one. Call signs in aviation are derived from several different policies, depending upon the type of flight operation, in most countries, unscheduled general aviation flights identify themselves using the call sign corresponding to the aircrafts registration number.
In this case, the sign is spoken using the International Civil Aviation Organization phonetic alphabet. Aircraft registration numbers internationally follow the pattern of a country prefix, for example, an aircraft registered as N978CP conducting a general aviation flight would use the call sign November-niner-seven-eight-Charlie-Papa. However, in the United States a pilot of an aircraft would normally omit saying November, at times, general aviation pilots might omit additional preceding numbers and use only the last three numbers and letters. This is especially true at uncontrolled fields when reporting traffic pattern positions, for example, Skyhawk eight-Charlie-Papa, left base
Forty-eight of the fifty states and the federal district are contiguous and located in North America between Canada and Mexico. The state of Alaska is in the northwest corner of North America, bordered by Canada to the east, the state of Hawaii is an archipelago in the mid-Pacific Ocean. The U. S. territories are scattered about the Pacific Ocean, the geography and wildlife of the country are extremely diverse. At 3.8 million square miles and with over 324 million people, the United States is the worlds third- or fourth-largest country by area, third-largest by land area. It is one of the worlds most ethnically diverse and multicultural nations, paleo-Indians migrated from Asia to the North American mainland at least 15,000 years ago. European colonization began in the 16th century, the United States emerged from 13 British colonies along the East Coast. Numerous disputes between Great Britain and the following the Seven Years War led to the American Revolution. On July 4,1776, during the course of the American Revolutionary War, the war ended in 1783 with recognition of the independence of the United States by Great Britain, representing the first successful war of independence against a European power.
The current constitution was adopted in 1788, after the Articles of Confederation, the first ten amendments, collectively named the Bill of Rights, were ratified in 1791 and designed to guarantee many fundamental civil liberties. During the second half of the 19th century, the American Civil War led to the end of slavery in the country. By the end of century, the United States extended into the Pacific Ocean. The Spanish–American War and World War I confirmed the status as a global military power. The end of the Cold War and the dissolution of the Soviet Union in 1991 left the United States as the sole superpower. The U. S. is a member of the United Nations, World Bank, International Monetary Fund, Organization of American States. The United States is a developed country, with the worlds largest economy by nominal GDP. It ranks highly in several measures of performance, including average wage, human development, per capita GDP. While the U. S. economy is considered post-industrial, characterized by the dominance of services and knowledge economy, the United States is a prominent political and cultural force internationally, and a leader in scientific research and technological innovations.
In 1507, the German cartographer Martin Waldseemüller produced a map on which he named the lands of the Western Hemisphere America after the Italian explorer and cartographer Amerigo Vespucci
Sutro Tower is a 977 ft three-pronged TV and radio antenna tower in San Francisco, California. Rising from a hill between Twin Peaks and Mount Sutro near Clarendon Heights, it is a prominent feature of the city skyline and a landmark for city residents and visitors. Before the construction of Sutro Tower in 1973, television reception in San Francisco was spotty because the hills of the city blocked the line-of-sight television signal. The great height of the new tower helped to resolve that problem, transmitters had been scattered throughout the Bay Area, including at San Bruno Mountain, Mt. Allison, Monument Peak, and Mt. Diablo. Local residents opposed the tower even before it was completed, including criticism of the effect the tower would have on the rest of San Francisco. San Francisco writer Herb Caen once wrote, I keep waiting for it to stalk down the hill, acknowledging both displeasure and affection for its undeniable prominence on the citys skyline, it is sometimes referred to light-heartedly as the Sutro Monster or Space Claw.
When first built, the legs of the tower were illuminated at night with long tubes of white light that looked like long fluorescent tubes. However, public outcry resulted in the lights being removed soon after they were turned on, the tower is featured in video games, business logos, on clothing, as furniture and even tattoos. The U. S. band Information Society used it on the cover of their album Dont Be Afraid, a local entertainment guide, SF Station, uses it as a logo, as does the collaborative art game SFZero and the Expose SF art competition. Construction commenced in 1971 by Kline Towers of Columbia, South Carolina, approximately 3,750 m3 of concrete were used to make the foundation of the 3.7 million pound tower. Earthquake proofing includes ballasting two-thirds of the weight of the structure below ground and it is used to transmit the signals of eleven television stations and four FM radio stations and for various other communications services. Sutro Tower leases space to other Bay Area radio and television stations, including PBS outlet KQED, independent station KOFY-TV, and KBCW, a sister station to KPIX.
Three other major Bay Area TV stations are unable to be located at Sutro Tower—the NBC-owned duopoly of KNTV and KSTS and those locations allow these stations to maintain primary coverage over San Jose and the South Bay—San Jose is the city of license for all three stations. The tower stands 297.8 m above ground and 552 m above sea level and it is the tallest structure in the city, surpassing the 258.4 m Transamerica Pyramid by more than 39 m. The old site of the Sutro Mansion, and thus the land on which the stands, is owned by Adolph Sutros descendants. The facility is only by authorized vehicles. The area near the site offers beautiful panoramic viewpoints of San Francisco, there is a platform near the top of the tower,232 m above ground and 486.2 m above sea level. Only authorized maintenance workers can access the tower via a small two-person elevator that runs inside the west tower enclosed leg, there is no public access within the Sutro Tower property lines